Inorganic Approach to Stabilizing Nanoscale Toroidicity in a Tetraicosanuclear Fe$_{18}$Dy$_{6}$ Single Molecule Magnet

Cyclic coordination clusters (CCCs) are proving to provide an extra dimension in terms of exotic magnetic behavior as a result of their finite but cyclized chain structures. The Fe$_{18}$Dy$_{6}$ CCC is a Single Molecule Magnet with the highest nuclearity among Ln containing clusters. The three isostructural compounds [Fe$_{18}$Ln$_{6}$(μ-OH)$_{6}$(ampd)$_{12}$(Hampd)$_{12}$(PhCO$_{2}$)$_{24}$](NO$_{3}$)$_{6}$·38MeCN for Ln = Dy$^{III}$ (1), Lu$^{III}$ (2), or Y$^{III}$ (3), where H$_{2}^{-}$ampd = 2-amino-2-methyl-1,3-propanediol, are reported. These can be described in terms of the cyclization of six {Fe$_{3}$Ln(μOH)(ampd)$_{2}$(Hampd)$_{2}$(PhCO$_{2}$)$_{4}$}$^{+}$ units with six nitrate counterions to give the neutral cluster. The overall structure consists of two giant Dy$_{3}$ triangles sandwiching a strongly antiferromagnetically coupled Fe$_{18}$ ring, leading to a toroidal arrangement of the anisotropy axis of the Dy ions, making this the biggest toroidal arrangement on a molecular level known so far.